Antenna for radio communication



l N. E. LINDENBLAD ANTENNA FOR RADIO COMMUNICATION n 9 l 9.. l m s FiledDec. 24, 1928 vwantoz uns E LINDEN BLAD N N ANN N NW Patented Sept. 19,1933 UNITED STATES PATENT OFFICE Nils E. Lindenblad, Port Jeierson, N.Y., assignor to Radio Corporation of America, a corporation of DelawareApplication December 24, 1928 Serial No. 328,147

24 Claims.

This invention relates to antennas for radio communication.

Short wave antennas suffer from the disadvantage of having to be rathercritically tuned to the working frequency, and from the furtherdisadvantage of necessitating the use of some kind of an impedancematching device between the an- Tenna and the transmission lineconnecting the antenna with the radio equipment. It is an object of myinvention to provide an exceedingly simple form of short wave antennawhich will operate over a considerable range of frequency, and a furtherobject of my invention is to provide an' antenna with which atransmission line may pedance matching devices.

My antenna consists simply of a pair of conductors which at one end arespaced at the spacing of the transmission line, and are coupledthereto," and which gradually diverge to a much wider spacing at theirother ends. In effect, therefore, the antenna consists merely of agraciually diverging extension of the conductors of the transmissionline, and, in one aspect, the invention resides in the discovery thatradiation may be obtained from a transmission line by graduallyincreasing the spacing between the wires of theline.

The desired radiation takes place in the direction of the axis of thepair of conductors, and is caused by the expansion of the current or thetravelling wave of energy in the conductors. Reection will cause astanding Wave, instead of a travelling wave, and result in radiationsideways from the antenna. Despite this, the radiation in the directionof the antenna is still considerably greater than that obtainable from asimple doublet. However, as a refinement the harmonic radiation may belessened by reducing the standing waves, and to so do is a furtherobject of my invention. It is not feasible, in the case of atransmitting antenna, to avoid standing waves by closing the end of theantenna with a surge resistance, because of the excessive losses whichwould take place therein.

To lessen the standing wave I reduce the reected energy by radiating asmuch of the energy fed to the antenna as possible. To merely increasethe dimensions of the antenna is not practicable, for to increase thelength without increasing the spacing, that is, to decrease the angle ofdivergence, does not increase the radiation, and on the other hand, tokeep the same angle of divergence necessitates so wide a spacing as tomake the antenna structurally inconvenient. To overcome this I employ aplurality of antennas or pairs of diverging conductors, arranged end toend, so as to radiate cumulatively.

I have also found that a pair of converging conductors, like a pair ofdiverging conductors,

be coupled without the use of intermediate im,

(Cl. 25H3) will radiate energy, but this radiation is in opposite phase.The antenna may therefore comprise a plurality of pairs of conductorswhich successively diverge and converge, with means coupling theantennas which reverse the phase of the energy fed thereto.

While the terminology employed in the foregoing description may applymore particularly to a transmitting antenna the structure set forth isequally useful as a receiving antenna.

The invention is further described in the following specication, whichis accompanied by a drawing in which Figure 1 represents one form of myinvention;

Figure 2 is a modification employing straight conductors;

Figure 3 shows the use of a plurality of diverging and convergingantennas;

Figure 4 is a section of Figure 3 taken on the line 4-4; and

Figure 5 is a modification of Figure 3 showing an alternative form ofphase reversing coupling means between the successive antennas.

Referring to Figure 1 it will be seen that the antenna consists of apair of conductors 2, 4, which are connected to a transmission line 6 atpoints 8 and 10, which are spaced at the spacing of the transmissionline. From the points 8 and l0 the conductors 2 and 4 gradually divergeto a much wider spacing at the ends 12 and 14. The extension of theconductors may be curved, as shown, and one form which is quitesuccessful in operation is an expansion according to an exponential law.

However, in actual practice I find that the refinement of an exponentialcurve is not essential, and that the conductors 2 and 4 may be straightconductors strung between the points 8 and 12, and the points 10 and 14,under direct tension, and without the use of intermediate shaping or guywires, and such an arrangement has been indicated in Figure 2.

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No impedance matching device is necessary y with this antenna, so thatin actual practicethe antenna is exceedingly simple to erect, it beingnecessary merely to provide a pair of support- ,ing points 12 and 14 ata desired distance from the termination of the transmission line, andthen to continue the conductors of the transmission line directly to thespaced points 12 and 14.

Whatever amount of energy has not been radiated when the travelling wavereaches the end of the antenna is reiieoted, and thus causes a partialstanding wave, which will extend back along the transmission line 6. Ifthe trans-v mission line is short, this may be neglected, but if thetransmission line is long, and the antenna is relatively small, so thatonly a small portion of the energy is radiated, it may prove desirableto employ an impedance matching device between the transmission line andthe antenna, as is indicated by the impedance matching unit 16, shown inFigure 2.

If, instead, the antenna is made to radiate more energy, the standingwave will incidentally be reduced, and the impedance matching device maybe dispensed with. To merely make the antenna much longer, while keepingthe same spacing at its open end, does not help, because such aprocedure merely slows up the rate of spread of the energy, and does notincrease the quantity of energy radiated. On the other hand itordinarily is not structurally possible to make the antenna considerablylonger while maintaining the same angle of divergence of the conductors,owing to the great spacing which would be needed at the open end of theantenna. The same result may be accomplished Without these disadvantagesby using a plurality of antenna sections arranged'end to end. Since aconverging antenna is similar in operation to a diverging antenna,except for a reversal in phase, it becomes especially convenient to usea plurality of antenna sections which are successively diverging andconverging, and such antennas have been indicated in Figures 3 and 5.

Referring to Figure 3 it will be seen that a transmitter 20 is coupledto a diverging antenna 22 by a transmission line 24. The divergingantenna 22 is followed by a converging antenna 24, which is coupled tothe diverging antenna 22 by a pair of conductors 26 and 23. The spacingbetween these conductors is kept constant, so that practically noradiation takes place there from, but at the same time the conductorsare electrically crossed in order to reverse the phase of the energybeing fed from antenna 22 to antenna 24. For this purpose each of theconductors is supported, at least approximately, in the form of a helix,a feature which is more clearly indicated in the section taken on theline and constituting Figure fr. The pitch of the helices should besufiiciently great that the physical distance in space between theantennas 22 and 2a is substantially equal to the distance along theconductors 26 and 2S, so that the phase displacement of the wavetravelling in space will coincide with that of the energy wavetravelling on the conductors 26 and 28. The converging antenna 24 isfollowed by a diverging antenna 30, and the adjacent ends of theantennas 24 and 30 are coupled by phase reversing coupling conductors 32and Se.

A modification of the arrangement shown in Figure 3 is indicated inFigure 5, in which a transmitter 20 is coupled by a transmission line 24to a diverging antenna 22, followed by a converging antenna 24, which inturn is followed by a diverging antenna 30, much as in Figure 3.However, in this case the antennas 22 and 24 arecoupled by conductors 40and 42, which are a half wave in length, in order to reverse the phaseof the energy iiowing therethrough, and which are bent back uponthemselves so as to be substantially nonradiating. The connectionbetween the antennas24 and 30 is made simply by crossing the conductors,as shown, the conductors being separated slightly at the crossing pointby an insulator in order to prevent a short circuit between theconductors. in the arrangements shown in Figures 3 and 5 any desirednumber of antenna sections may be employed.

The plane of polarization of the radiated energy coincides with theplane of the conductors, so that if the conductors are positioned in ahorizontal plane the energy is radiated with horizontal polarization,and if the conductors are positioned in a vertical plane the energy isradiated with vertical polarization.

With the conductors inl a horizontal plane a standing wave tends tocause side radiation. By locating the conductors in a vertical plane thedirectivity in azimuth may be maintained regardless of the presence ofstanding waves, but even in such case it is desirable to prevent wasteof the energy radiated thereby, and it is therefore desirable to makethe length of the-conductors or the number of antenna sectionssuiciently great, in accordance with the foregoing instruction, toreduce the standing wave.

In connection with Figures 3 and 5, the desired radiation will, ofcourse, take place in the direction of the axis of the transmission line24 and the diverging conductors. Taken from another point of view. wecan consider merely the upper half of Figures 3 and 5 as being in avertical plane with its'image in the ground; we will then have twoserially connected conductors (conductor 26 and the upper antennaleading to transmission line 24 in Figure 3). Radiation will occursubstantially in the direction of a line perpendicular to the bisectorof the angle between these two conductors.

It will be understood by those skilled in the art that ii improveddirectivity is desired a plurality of these antennas may be employedabreast or in broadside, that is to say, collaterally spaced apart inparallel formation along a line at right angles to the desired directionof communication.

Since the preferred radiation is from the travelling wave, and is due tothe expansion of the lines of force between the current chargestravelling along the conductors, the divergence should preferably befairly gradual, and the spacing at the open end, while variable over agreat range, should be in the neighborhood of a fth of the length, andthe length of each antenne. section should be of the order of magnitudeof ve to ten waves long.

The antenna is equally suitable both for transmission and reception, theenergy in the latter case being collected and converged into thetransmission line without the necessity of an impedance matching device.

I claim:

l. The method of directively radiating or collecting high frequencyelectrical energy which includes directing energy of opposite polarityin a plurality of gradually diverging paths diverging and extendinglongitudinally in the desired direction of radiant action.

2. The method of unidirectionally radiating or collecting high frequencyelectrical energy which includes directing energy of opposite polarityin a plurality of gradually converging paths converging and extendinglongitudinally in the desired 'direction of radiant action.

3. The method of radiating or collecting high frequency electricalenergy which includes directing energy of opposite polarity successivelyin a plurality of gradually diverging and converging paths and phasereversing the energy as it is directed from one path into another.

4. A uni-directional antenna comprising a gradually diverging pair ofconductors excited in phase opposition, diverging and extendinglongitudinallyonly` in the desired direction 'of radiant action.

5. A uni-directional antenna comprising a gradually converging pair ofconductors excited in phase opposition, converging and extendinglongitudinally only in the desired direction of radiant action.

6. A uni-directional antenna comprising a pair of conductors excited inphase opposition, ex-

tending longitudinally in the desired direction of radiant action, 'theeffective portions of which gradually diverge and converge successively.

7. A uni-directional transmitting antenna' comprising a pair ofconductors excited in phase opposition, extending' longitudinally inthe. direction of desired transmission, the radiating portions of whichgradually diverge and converge successively in the direction of desiredtrans-` mission.

8. In combination, a two conductor transmission line excited in phaseopposition, and an antenna connected thereto extending longitudinally inthe direction of transmission, comprising a gradually divergingextension of the conductors of the transmission line at their remoteopen ends.

9. In combination, a two conductor transmission line excited in phaseopposition, and an antenna extending longitudinally in the direction ofdesired radiant action comprising an open ended pair of conductors whichat one end are spaced at the spacing of the transmission line and arecoupled thereto, and which gradually divasrge to a much wider spacing attheir open en 10. In combination, a transmission line, and an antennaextending longitudinally in the directionl of desired radiant actionconnected thereto comprising a pair of open ended conductors of theorder of magnitude of a number of wave lengths long which are widelyspaced at the ends remote from the transmission line and energized withenergy of opposite polarity, and spaced at the spacing of thetransmission line at their junction therewith.

11..A uni-directional antenna comprising a plurality of pairs ofgraduallydivergingmonductors extending longitudinally in the directionVof desired transmission and energized in phase opposition.

12. In combination, a transmission line, an antenna connected theretocomprising a pair of conductors a number of wavelengths long which arespaced at the spacing of the transmission line at their junctiontherewith, and which gradually diverge to a much wider spacing at theirremote ends, a second antenna vcomprising a pair of conductors a numberof wave lengths long arranged in extension of the first antenna, andwidely spaced at their near ends and closely spaced at their remoteends, another diver'ging antenna arranged in extension of the convergingantenna, and phase reversing means for coupling said antennas together.

13. A uni-directional'antenna comprising a diverging pair of conductorsexcited in phase opposition, diverging only in the desired direction ofradiant action.

14. A uni-directional antenna comprising a converging pair of conductorsexcited in phase opposition, converging only yin the desired directionof radiant action.

15. A uni-directional antenna comprisingl a pair of conductors excitedin phase lopposition, extending longitudinally in the desired directionci.' radiant action, the effective portions of which diverge andconverge successively.

16. A highly directional antenna system comprising wires which are longrelative to the length of the communication wave excited in phaseopposition, which rst diverge from the excita-' tion-end and thenconverge successively, whereby'radiant action occurs predominantly in adirection substantially through the opposite apices of the wires.

17. A system in accordance vwith claim 16, characterized in this, thatsaid wires are in a single vertical plane.

18. A highly directional antenna system comprising a pair of conductorsexcited in phase opposition, said wires being long relative to thelength of the communication wave and extending in the desired directionof radiant action, the effective portions of which diverge and convergesuccessively.

19. A highly directional antenna system comprising a pair of conductorsangularly disposed with respect to each other,l said conductors beinglong relative to the length of the communication wave and open-ended,and means for exciting the conductors in phase opposition wherebyradiant action occurs predominantly along the-direction of the axis ofthe conductor system.

20. A unidirectional antenna system comprising a diverging pair ofconductors, the said conductors being long relative to the length of thecommunication wave, and means for producing traveling waves thereonwhereby radiation is predominantly along the approximate direction ofthe length of the conductor system.

21. A system in accordance with claim 20 characterized in this, thatsaid conductors are openended and disposed in the same vertical plane.

22. A directional antenna comprising a diverging pair of conductorswhich are long relative to the working wave length, andV means atadjacent ends of said conductors for energizing same in phaseopposition, said conductors being arranged to be on the same side ofsaid energizing means and to extend away from said energizing meanswhereby radiant action occurs 'predominantly along the approximatedirection of the length of the conductor system.

23. A directional antenna comprising a pair of open-ended, divergingconductors which are long relativeto the working wave length, and meansat adjacent ends of said conductors for energizing samein phaseopposition, said conductors being arranged to be on the same side of andto extend away from said energizing means whereby radiant action occurspredominantly in a dir'ection making. equal angles greater than zerodegrees with reference to said conductors.

24. A highly directional antenna system comprising al pair of electricalconductors which are disposed at an angle with respect to each other andserially connected together, said conductors having an overall lengthwhich is long relative to the operating wave length, high frequencyapparatus, and means for connecting said apparatus to one end of one oi'said conductors, the other end of said connected conductor beingconnected to one end of the second conductor of said pair whereby highfrequency energy flows through the entire length of one conductor andcontinues serially through the entire length of the other conductor, theconductors being adjusted pendicular to the bisector of the anglebetween said conductors.

NILS E. IINDENBLAD.

DISCLAIMER 1,927,522.Nils E. Lindenblad, Port Jefferson, N. Y. ANTENNAFon RADIO Con- MUNICATION. Patent dated September 19, 1933. Disclaimerled September 24, 1940, by the assignee, Radio Corporation of America.Hereby enters this disclaimer to claim 24 of said Letters Patent and tolines 96 to 105 of pa e 2 of the specification.

[omu Game october ze, 1940.]

